The present invention concerns a type of plastic frame for transparencies and also relates to means for placing positive film in the frame.
As is known in the art, a "transparency" is a positive film mounted in a frame, generally intended to be projected on a screen. Originally, the frames were of self-gluing cardboard, which had substantial drawbacks including susceptibility to being damaged and "dog-eared" and not being capable of repeated use.
An alternative proposed construction is to make such frames of plastic. Initially it was proposed to use two independent frames which could be clipped together, thereby enclosing the positive film. As a consequence, the placing of the film in position is laborious and the clipping is at times difficult. In order to assure better cohesion between the frames, they can be glued or heat-sealed which, unfortunately, does not permit them to be disassembled and used again. More recently, it has been proposed to use two clippable hinged frames. However, the drawbacks remain substantially the same.
In U.S. Pat. No. 3,069,795 there is disclosed a single-piece frame of plastic having a window-shaped opening on the edges of which horizontal grooves located in the plane of the film extend in order to facilitate the introduction of the film.
In this type of frame: (1) the length of the window opening on the side located in front of the plane of the film is greater than the length of the film to be inserted, (2) the length of the side located on the back of the film however, is less than the length of this film, and (3) the end of the grooves for receiving the film forms an abutment for the film while the distance between the ends of these grooves is at least equal to the width of the film. The placing of positive films in this type of frame, which has been successfully marketed to amateurs, is effected by means of a small manual tool especially adapted for this purpose and very easily produced. Such a tool is described in French Pat. No. 2,308,124, corresponding to U.S. Pat. No. 3,996,683. Unfortunately, this type of frame and this tool do not make it possible to economically position several hundred transparencies a day, particularly because this frame does not permit the automation of these operations.
The present invention relates to an improved frame of the type in question which makes it possible to automate the positioning of the positive films and which can be economically used in semi-professional or even industrial operations. The present invention also relates to devices for manually and automatically placing the films into the frames. Automatic devices for the placing of transparencies in frames are known. In general, these devices are complicated, expensive, bulky and do not permit economical operation for small series or individual processing. The automatic device of the invention overcomes these drawbacks.